Sounds like you're set then.
I'm surprised you can't find a 1/2-ton frame reasonably, since I have cut up two of them in the past year because no one wanted them, and I know where two more are that could be had cheap. Of course they would not be cheap to you being so far from here.
Do you have a 9-foot 1-ton type box? Be a shame to cut those sides, because there are people, including me, who would love to have them and they aren't reproduced anywhere.
Here is an outrageous thought. The Camaro subframe is really just a touch wide under one of these trucks, but a g-body ('78 to '88 Monte Carlo and similar) is the right width in the front. It's a perimeter type frame, but if you used just the front suspension and fabricated the rest of the frame, you could design for a 1/2-ton wheelbase and not deal with the issues of the 1-ton frame. You would be doing some fabricating...
Most El Camino frames are perimeter type and that does create problems since that type of frame is almost always too wide under the cab, often putting the side rails under the running boards.
Have you considered an S-10 frame? A standard cab long box is just the right length. They are a little narrow front and rear, which is nice if you are lowering the truck. In the rear a Camaro or S-10 4x4 axle are about right width.
But then if you are not afraid of using those tools, I see no reason not to swap the 1/2-ton front axle under your 1-ton truck. You just won't have the 1-ton capacity any more.
I also have a 3 bay shop too, but only two welders. Mine is crowded by projects and becoming way too small. My brother has a machine shop in his basement, but so far that hasn't helped me much.
